1. Field of Invention
The invention relates to a voltage regulator and, in particular, to a source and sink voltage regulator.
2. Related Art
The development in electronic products has the trend of miniaturization and, therefore, complicated and delicate structures. The voltage stability and the response time to load variation of the power supply are two primary issues that concern researchers in the field. The size of devices directly affects the costs and profits of the manufacturers.
In order to ensure the stability of the voltage, the so-called voltage regulator is invented to maintain a predetermined normal output voltage. The voltage regulator may have different forms, such as a device form on large apparatus or a chip form on a circuit system. However, some conventional voltage regulators for the circuit system cannot draw a reverse loading current. Therefore, when the equivalent external loading voltage is too high, there is no way to lower it by drawing the current. Those voltage regulators with the function of outputting and drawing currents, on the other hand, have the problem of a slow response time. This is because when the voltage regulator changes from current output to current drawing, or vice versa, it always involves turning on some shutdown circuits. Such initialization of the shutdown circuits is the cause of delay in response time.
In addition, the output circuits of some conventional voltage regulators are composed of N-type metal oxide semiconductor (MOS) and P-type MOS. However, the P-type MOS has a lower drive capability. Therefore, one needs a larger chip area in order to provide the required current output. In summary, the properties of the voltage regulator can be improved if the chip area and the response time can be reduced at the same time.